Apparatus for taking tomograms of parabolically curved objects

ABSTRACT

For taking tomograms of parabolically curved objects such as the dentition, jawbones and other bony structures of the head and dento-facial region, there are provided an X-ray tube and a radiographic film holder at both ends of a turnable arm. This arm is furnished with a plurality of shafts alternately serving as a pivot therefore, in such a manner that the X-ray tube supported at one end of the arm turns round a parabolically curved object at an unvarying distance therefrom, while radiating X-rays which traverse the object to impinge upon the radiographic film carried by the aforesaid holder turning in coordination with the turn of the arm. There are also disclosed herein a device for holding the head of a patient, a device for minute adjustment of ear-rods and the like for use in positioning the head, and a device for modification of the image density of X-rays traversing the head in readily penetrable directions.

United States Patent 1 1 1111 3,737,660

Ando et al. 14 1 jam 5, 31973 54 APPARATUS FOR TAKING 3,514,606 5 1970Rabey 1. ..250/65 R TOMOGRAMS 0 PARABOLIC ALLY 2,630,536 3/1953 Vladeff..250/65 R CURVED OBJECTS [75] Inventors: Shoichi Ando, Shibuya-ku,Tokyoto; Shinji Yoshioka, Ichikawa-shi, both of Japan Assignee: HidaDenki Kogyo Kabushiki Kaisha, a/k/a Mida Electronic Apparatus IndustrialCo., Ltd., Tokyo, Japan; a part interest Filed: Oct. 7, 1970 App]. No.:78,666

[30] Foreign Application Priority Data Feb. 19,1970 Japan ..45/16790Dec. 12, 1969 Japan ..44/118085 Dec. 1, 1969 Japan ..44/114226 Oct. 9,1969 Japan ..44/80982 [52] U.S. Cl ..250/50, 250/61.5, 250/65 R [51]Int. Cl. ..G03b 41/16 [58] Field of Search ..250/65 R, 50, 61.5

[56] References Cited UNITED STATES PATENTS 3,536,913 10/1970 Huchel..250/65 R Primary Examiner-James W. Lawrence Assistant ExaminerC. E.Church Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT Fortaking tomograms of parabolically curved objects such as the dentition,jawbones and other bony structures of the head and dento-facial region,there are provided an X-ray tube and a radiographic film holder at bothends of a turnable arm. This arm is furnished with a plurality of shaftsalternately serving as a pivot therefore, in such a manner that theX-ray tube supported at one end of the arm turns round a parabolicallycurved object at an unvarying distance therefrom, while radiating X-rayswhich traverse the object to impinge upon the radiographic film carriedby the aforesaid holder turning in coordination with the turn of thearm. There are also disclosed herein a device for holding the head of apatient, a device for minute adjustment of ear-rods and the like for usein positioning the head, and a device for modification of the imagedensity of X-rays traversing the head in readily penetrable directions.

6 Claims, 15 Drawing Figures PATENIEBJ'JH 5 191a SHEET E OF 6 FIGSAPPARATUS FOR TAKING TOMOGRAMS OF PARABOLICALLY CURVED OBJECTSBACKGROUND OF THE INVENTION This invention relates generally totomography, and in particular to a novel apparatus capable of takingtomograms of objects in the shape of an approximately parabolic curvesuch as a panoramic view, especially, the dentition, jawbones and otherparts of the face and head. The invention also relates to someimprovements designed to add to the utility of the above apparatus.

There has long been awaited by roentgenologists and related specialiststhe advent of apparatus capable of taking curved surface tomograms ofthe dentition, jawbones, etc., of the face and head. Many attempts madeconventionally at the provision of such apparatus have been frustrated,in nearly all cases, due to the fact that those bony structures in thehuman face and head represent a parabolic curve consisting of two ormore arcs of different curvatures.

Another difficulty resides in the correct adjustment and holding of thehead at a position of the greatest convenience for tomographicexamination. It has also been considered no less difficult toappropriately modify the unsubdued image density of X-rays radiatedthrough the head in its readily penetrable directions. These intenseX-rays will cause unevenness in the tone of a radiographic film exposedthereto.

Hence, no satisfactory tomograms of the dentition, jawbones and otherdesired objects in the face and head have so far been obtainable.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a novel apparatus capable of taking clearand well-defined panoramic tomograms of tbe dentition, jawbones andother parabolically curved objects.

Another important object of the invention is to provide a device forholding the head of a patient at a minutely adjusted and visuallyconfirmed position of the greatest convenience for its tomographicexamination.

Still another important object of the invention is to provide a devicecapable of preventing, as far as feasible, the unevenness in the densityof a radiographic film produced by undesired changes in the intensity ofX- rays depending upon the arrangement of bony structures or aircavities present in the head.

With these objects in view and the other objects hereinafter set forth,the invention will now be described in detail with connection to theaccompanying drawings showing several preferred embodiments thereof, inwhich like reference characters indicate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS of the operating principles of theapparatus in accordance with the present invention;

FIGS. 3, 4 and 5 are similar diagrams in which the FIG. 6 is a top viewof a device for turning an X-ray tube and a radiographic film holder ofthe apparatus of the invention along a parabolically curved object, theX-ray tube and the radiographic film holder being in positions shown inFIG. 2;

FIG. 7 is a vertical sectional view of the device of FIG. 6;

FIG. 8 is a top view of the device of FIG. 6, with the X-ray tube andthe radiographic film holder in positions shown in FIG. 4;

FIG. 9 also is a top view of the device of FIG. 6, with the X-ray tubeand the radiographic film holder in positions intermediate between thoseshown in FIGS. 3 and FIG. 10 is a front elevational view of a headholding device in the apparatus of the invention;

FIG. 11 is a side elevational view of the head holding device of FIG.10;

FIG. 12 is a top view of the head holding device of FIG. 10;

FIG. 13 is a perspective view of a device for adjustment of ear-rods foruse in holding the head of an individual to be tomographically examinedby the apparatus of the invention;

FIG. 14 is a sectional view of one of the ear-rods shown in FIG. 13; and

FIG. 15 is a top view showing the arrangement of filter means adapted tomodify the intensity of X-rays traversing the head in readily penetrabledirections.

DETAILED DESCRIPTION OF THE INVENTION It will redound to the fullappreciation of the present apparatus to clarify the concepts supportingit. So, first of all, description is given on how a tomogram of aparabolically curved object with two or more arcs of differentcurvatures can be taken with reference to FIGS. 1 through 5.

A parabolic curve 3 shown in perspective in FIG. 1 represents thedentition, jawbones and other objects in the head of an individual, andsaid parabolic curve 3 is indicated by broken lines in FIGS. 2 through5. Let it be assumed that the parabolic curve 3 consists of an arc A2-A3having its center at a point 7 and a radius of r2, an arc A3-A4 havingits center at a point 6 and a radius of r1, and an arc A1-A2 having itscenter at a point 8 and a radius r1.

Now, referring to FIG. 2, an arm 42 is disposed as illustrated which hasan X-ray tube 1 at one end and at the other end a screen 5 having a slit4 therethrough in order to permit the passage of a beam of the X-raysemitted from a slitted opening of the X-ray tube 1. Inside the screen 5there is provided a radiographic film holder 2 so as to be turnable inthe arrow marked direction al in coordination with the turn of the arm42 in the arrow marked direction a2. Hence, a tomogram of the arc Al-A2can be taken as the arm 42 turns on its pivot 8 in the clockwisedirection a2 to a position shown in FIG. 3 while the radiographic filmholder 2 also turns in the clockwise direction al in coordinationtherewith. Then, with the arm 42 at the position shown in FIG. 3,another pivot of the arm 42located at a point x which is at a distance(r1 r2) from the center 8 of the arc Al-A2 is adjusted at the center 7of the arc A2-A3, a tomogram of which is obtainable by turning the arm42 on the above adjusted pivot 7 to the position given in FIG. 4. Atthis position, the first mentioned pivot of the arm 42 which was locatedat the center 8 in FIG. 3 is now brought to the center 6 of the arcA3-A4, so that a tomogram of this are A3-A4 can be taken by turning thearm 42 on this same pivot at 6 to the position of FIG.5 while alsoturning the film holder 2 in the same clockwise direction.

In this manner, a series of tomograms of the parabolic curve 3consisting of the arcs Al-A2, A2-A3 and A3A4 can be taken by turning thearm 42 pivoted at the successive ones of the centers 8, 7 and 6 of thosearcs. Described in the following, with reference to FIGS. 6 through 9,is a device for so turning the arm 42, as adapted for materialization ofthe foregoing fundamental concepts of the present invention.

As seen in the drawings, the arm 42 is turnably supported on a disk 43by means of self-aligning ball bearings 43a and is provided with twovertical shafts 8a and xa at positions corresponding to the center 8 ofthe arc A1-A2 and the point x of FIG. 2. Further, at the midpart of thedisk 43, there is provided a hole 44 therethrough, so shaped as toconsist of three arcs drawn round the aforesaid centers 6, 7 and 8 ofthe arcs A3-A4, A2-A3 and Al-A2. A means 45 (for example, a spring) isprovided whereby either one of the vertical shafts 8a and xa istemporarily secured to the disk 43 as desired. Roller or ball bearings46 are provided at the lower ends of the vertical shafts 8a and xa so asto be in internal comtact with the hole 44. At one end of the arm 42there is provided an X-ray tube 1 having a slit Ia through which X-raysare emitted, while at the other end there is provided a screen having acorresponding slit 4 through which the X-rays are admitted to a filmholder 2 supported by the screen 5 so as to be turnable in coordinationwith the turn of the arm 42.v The desired turn of the arm 42 is obtainedby means of a motor M installed upon a motor base 48 slidable inaccordance with the turn of the arm 42 along a guide 47 upon the arm 42.The rotation of the motor M is conveyed, via bevel gears G2 and G3 and ashaft 49, to a pinion G4 which is in mesh with a ring gear G1. The shaft49 is provided with a roller 50 which is rotatable in internal contactwith the ring gear G1, while a shaft 51 secured to the motor base 48 isprovided with a roller 52 which is rotatable in external contact withthe same ring gear G1, so that these rollers 50 and 52 sandwich the ringgear G1 there-between. Accordingly, even though the arm 42 will turn oneither one of its pivots located at the points 6, 7 and 8 that are offthe center of the ring gear G1, the motor M slides by the turn of thearm 42 to such a position that the ring gear G1 is kept in constant meshwith the pinion G4.

To explain the operations of the above described device of theinvention, the vertical shaft 80 of the arm 42 is secured, while theother shaft xa is free to move,

when the arm 42 is at its starting position shown in FIG.

6. The rotation of the motor M set in motion, then, is conveyed to thepinion G4, as already mentioned. By the rotational force of this pinionG4, which is in mesh with the ring gear G1, the arm 42 starts turningclockwise, in FIG. 6, to a position shown in FIG. 8, while taking atomogram of the arc Al-A2 on a radiographic film carried by the holder2.

At the position of FIG. 8, the shaft xa of the arm 42 is located at thecenter 7 of the arc A2-A3 (because the distance between the shaft 8a andthe shaft xa is equal to a difference between rl and r2). Hence, byresuming the rotation of the motor M upon securing the shaft xa andreleasing the shaft 8a, the arm 42 similarly starts turning round theshaft xa due to the rotational force obtained by the intermeshing of thepinion G4 and the ring gear GI, past the position of FIG. 9, untilholder 2. Now, with the shaft 8a of the arm 42 located at the center 6of the arc A3-A4, this shaft 8a is secured while the other shaft xa isreleased, and the arm 42 is similarly turned round the shaft 8a to theposition shown in FIG. 5, thereby taking a tomogram of the final arcA3-A4.

It will now be clear how a complete tomogram of the arcs Al-A2, A2-A3and A3-A4 is obtained during the turn of the arm 42.

To elaborate further on the above described operations from a mechanicalpoint of view, the vertical shafts 8a and xa serving as a pivot for theturn of the arm 42 are secured alternately at the three points 6, 7 and8 (which are off the center of the ring gear G1) within the hole 44 ofthe disk 43. Consequently, as may be seen from FIG. 8, a distancebetween the pivot of the arm 42 and the intermeshing point of the ringgear G1 and the pinion G4 is subject to variation along with the turn ofthe arm 42. Should the motor M be installed fixedly on the arm 42,therefore, the pinion G4 would be meshed incompletely with the ring gearG1, either too deep or disengaged altogether therefrom, thus hamperingthe smooth turn of the arm 42. This is the reason why, according to thepresent invention, the motor M is installed on the motor base 48 whichis slidable along the guide 47 upon the arm 42 and, further, the ringgear G1 is provided with the two rollers 48 and 52 which are caused torotate in internal and external contact, respectively, therewith. Themotor M is thus enabled to adjust its position according to the radiusof the turn of the arm 42, while the pinion G4 is always kept in propermesh with the ring gear G1, so that the uninterrupted turn of the arm 42is insured.

While in the above described example of the device for turning the arm42 along an approximately parabolic curve in accordance with theconcepts of the invention, the ring gear G1 secured to the disk 43 iskept in constant mesh with the pinion G4 by means of the motor M that ismade slidable along the guide 47 upon the arm 42 simultaneously with theturn of this arm 42, the same purpose can also be accomplished bysecuring the ring gear G1 to the arm 42 and installing the motor M uponthe disk 43 so as to be slidable together with the turn of the arm 42.

The foregoing configurations make possible to take a series of tomogramsof the entire jawbones or the dentition of an individual, provided,however, that his head is held securely in position. Such a head holdingdevice in accordance with the invention will now be described withreference to an example illustrated in FIGS. 10 through 12.

As seen in the drawings, a casing 53 contains rails 54, and slidablymounted onthese rails 54 is a movable member 55 which is provided with athreaded rod 56 so as to be capable of being secured at a desiredposition and further with a pair of racks 57 and 58 (still to bedescribed with reference to FIG. 13) with their toothed surfaces opposedto each other. Between these racks 57 and 58 there is provided a pinion59 so as to.

rods 68 and 61 are provided downwardly at the opposite ends of the racks57 and 58, respectively, and these rods 60 and 61 are provided at theirlower ends with transparent ear-rods 63, 63 having flanges 62, 62 and soshaped as to fit in the outer orifice of the ear. A supporting portion64 (refer to FIG. 11) connected to the aforesaid casing 53 has a holdingmember 65 which is caused to be slidable toward and away from a column 9and to be stopped at any desired position in the course of its forwardand backward travels. The holding member 65 is attached with a chin rest68 which may include a vertical portion 66 and a horizontal portion 67.Further, this same holding member 65 is provided with an indicator means69, the graduations 70 for which are given on the supporting portion 64(refer to FIG. 12).

A bracket is supported by the aforementioned column 9 so as to bevertically movable. Adapters 71 and 72 for the ear-rods 63, 63 are soattached to the vertical rods 60 and 61 as to be freely movablethroughout the length thereof and to be fixed at any desired position,while these rods 60 and 61 are calibrated for indication of the heightsof those ear-rods 63, 63. An indicator means 73 provided to the movablemember 55 is for indication of its movements toward and away from thementioned column 9. A worm gear 74, on the same shaft as the aforesaidpinion 59, is in mesh with a worm 75 which is mounted on a manualrotation shaft 76 so as to be slidable along its length and also to berotated together with the shaft 76. These transmission means, however,may be served as well by bevel gears and the like. The manual rotationshaft 76 is provided with a handle 77. The aforesaid chin rest 68 isattached to the holding member 65 by means of a screw 78 so as to bevertically movable, to be fixed exactly at a desired position by meansof graduations 79 (refer to FIG. 10) calibrated on the holding member65. A head support 80 (refer to FIG. 11) cooperates with the ear-rods63, 63 and the chin rest 68 in order to set the head of a patient at acorrect position. This head support 80 is supported by means of anadapter 81 so as to be vertically movable, while the position of thisadapter 81 is made adjustable in directions toward and away from thecolumn 9 by means of a screw 82. As seen in FIGS. 10 and 12, the arm 42is provided at one end with the X-ray tube 1 and at the other end withthe radiographic film holder 2 and the screen 5, so as to be turnablealtogether.

The operations and functions of the head holding device, described inthe foregoing with reference to FIGS. 10, 11 and 12, are explainedhereinbelow.

For keeping the head of a patient at a proper position, the pinion 59 isfirst turned manually by means of the handle 77 thereby to adjust theracks 57 and 58 at their desired positions. Thus, upon insertion of theearrods 63, 63 into the earholes to a depth determined by their flanges62, 62, the head is now positioned without any sideways inclination. Thehead is then further readjusted as to its inclinations in front andrearward directions by means of the chin rest 68 which may consist ofthe vertical portion 66 and the horizontal portion 67. These simpleoperations are enough to position the head ready for its tomographicexamination, as well as to select desired planes in the head for thatpurpose repeatably.

Since the ear-rods 63, 63 are attached to the vertical rods 60 and 61secured respectively to the different ends of the racks 57 and 58 meshedwith one and the same pinion 59, the ear-rods are adjustablesimultaneously in coordinated movements by turning the handle 77 of thepinion 59. When the ear-rods are inserted into the earholes of apatient, his head is not only oriented in the proper direction withoutany sideways inclination but is located at the exact position fortomographic examination. In this case, if ear-rods 63, 63 are made of atransparent material, the ear-rods 63, 63 enable the examiner tovisually confirm if they are inserted properly into the earholes, eventhough they are provided with the flanges 62, 62. Further, according tothe present invention, the movable member 55 having all these racks 57and 58 and the pinion 59 is mounted on the rails 54 so as to be movabletoward and away from the column 9, so that the head held by the earrods63, 63 can be adjusted at a position most suitable for taking tomogramsof desired planes therein. Accordingly, a series of tomograms thus takenof a parabolically curved object are extremely clear and withoutsubstantially any duplex portions from one to the other. Furthermore,the exact positions of the movable member 55 and the chin rest 68 areclearly indicated on their respective graduations, so that, even when apatient is to have his head examined at intervals, the head can be setat the same position as before each time he sits for foregoing anothertomographic examination. It is accordingly possible to grasp with muchappropriateness the progress of a physical or pathological defect or adifference in its conditions before and after treat ment.

FIG. 13 illustrates another example of a means for the adjustment of thevertical rods 60 and 61 and, therefore, the ear-rods 63, 63 inaccordance with the present invention. In this example, as in theforegoing one shown in FIG. 10 in particular, the ear-rods 63, 63 havingflanges 62, 62 are provided at the lower ends of the vertical rods 60and 61. Further, in FIG. 13, the reference numeral 84 indicates abracket; 86 a holding portion; a shaft rotatably installed through theholding portion; 87 a turnable disk secured to the shaft 85; 88 holesformed on the upper surface of the disk 87; and 89 a fixing meansprovided to the holding portion 86 in order to fix the turnable disk 87by being inserted in one of its holes 88. Two parallel racks 57 and 58and, fixedly provided thereto, sliding portions 60a and 61a of thevertical rods 60 and 61 are slidably mounted on a guide 83 secured tothe bottom of the disk 87. Provided between these two racks 57 and 58 isa pinion 92 which is in mesh with both of the racks and which isprovided with a knob 93.

Thus, by appropriately turning the knob 93 of the pinion 92 in eitherdirection, the racks 57 and 58 and, therefore, the sliding portions 60aand 61a of the rods 60 and 61 move correspondingly in the oppositedirections so that the ear-rods 63, 63 may fit in the outer orifices ofthe earholes of a patient for the proper adjutment of his head.

Further, with reference to FIG. 14, the ear-rods 63 together with itsflange 62 is made of transparent material as in the foregoing example,and an electric lamp 90 supplied with power by means of lead wires 91 isinstalled therein. By the provision of this electric lamp 90, theoperator can adjust the knob 93 of the pinion 92 while visuallyinspecting the depth of insertion of the ear-rod 63 in the earhole of apatient. It will be needless to say that the provision of such anilluminating means only to one of the ear-rods is enough to serve theabove purpose.

Now, in taking tomograms of the dentition, jawbones and other objects inthe head as in the foregoing, consideration should also be given to thefact that such cavities present therein as the mouth, the nostrills andthe throad permit the penetration of too much X-rays more than otherpart when these are radiated in certain directions. The resultantlyproduced unevenness in the tone of a radiographic film containing aseries of tomograms prevent the physician from obtaining correctdiagnostic information therefrom. This defect, however, can beeliminated by another device of the invention newly introduced herein,in which filter means capable of limiting the penetration of X-rays isinstalled on the side of an X-ray tube and/or a radiographic film,thereby to obtain a tomogram of uniform tone.

An example of such a device will now be described in detail withreference to FIG. 15. A hood 94 made of transparent plastics permittingthe penetration of X- rays is supported by parts of the above describedhead holding device so as to enclose the jawbones 95, spinal column 96,dentition and other parts of the head as in the drawing. This hood 94 isattached with filter means 97 and 98 capable of limiting the penetrationof X-rays radiated, and made, for instance, of acrylic resin. Lackingthese filter means 97 and 98, more of the X-rays radiated in the arrowmarked directions over widths A and B, for example, would reach aradiographic film (disposed in front of the hood 94) than those radiatedin other directions, thus rendering the film portions impinged uponthereby darker than the rest and leaving indistinct images of thejawbones 95 and so forth thereon. This undesirable darkening of parts ofthe film can be successfully overcome by the device of the invention,with its acrylic-resin-made filter means 97 and 98 attached to the hood94, either on its inside or outside surface and either closer to theradiographic film or to the X-ray tube.

The filter means 97 attached to the open end of the hood 94, at the backof the spinal column 96 in FIG. 15, may be made outwardly openable bymeans of hinges 99. This helps a patient to move his head into and outof the hood 94.

It is also noteworthy that the above described device is capable ofgreatly reducing the high doses of X-rays administered hitherto to apatient throughout a series of radiating operations (from 10 to 14sheets of radiographic film for an adult) for the intraoralradiographing examination of his dentition.

Although several specific examples of the various devices proposed bythe present invention have been shown and described in the foregoing, itwill be obvious that many modifications, substitutions and changesthereof are possible. The invention, therefore, is not intended to berestricted by the exact showing of the drawings and the descriptionthereof but is considered to include other examples coming within thespirit of the invention.

We claim:

1. In apparatus equipped with a radiant rays source and a radiographicfilm holder thereby to take a tomogram of an object in the shape of anapproximately parabolic curve consisting of not less than two arcs ofdifferent curvatures; a head holding device comprising, in combination:

a column slidably supporting the head holding device proper;

a movable member mounted on a pair of rails within a casing so as to becapable of moving toward and away from said column, said movable memberhaving a means thereby to be secured at any desired position in thecourse of its travels;

a pair of racks disposed in side-by-side relationship across saidmovable member and having their toothed surfaces opposed to each other;

a pinion provided between said racks so as to be in mesh with both ofthem, said pinion having a means thereby to be turned manually fromoutside of said casing;

a pair of rods provided downwardly at the opposite ends of said racks,each of said rods having at the lower end a flanged ear-rods to beinserted into the outer orifice of the ear;

a chin rest provided to a holding member so as to be vertically movable,said holding member being installed in a supporting portion of saidcasing so as to be movable toward and away from said column and to befixed at any desired position in the course of its travels; and

a head support including means for adjustment of its position in bothvertical and horizontal directions.

2. A head holding device as claimed in claim 1, in which said holdingmember is provided with an indicator means, the calibrations for whichare given on said supporting portion, and said holding member isprovided with another set of calibrations for said chin rest connectedslidably thereto, whereby a setting of said chin rest in both horizontaland vertical directions can be read numerically.

3. A head holding device as claimed in claim 1, in which said flangedear-rods are transparent.

4. A head holding device as claimed in claim 3, in which illuminatingmeans are provided in the hollowed interiors of said transparent flangedear-rods.

5. A head holding device as ciaimed in claim 1, in which said movablemember is provided with an indicator means capable of indicating itsposition in directions toward and away from said column.

6. A head holding device as claimed in claim 1, in which said verticalrods are calibrated for indication of the heights of said ear-rodsprovided slidably thereto. l k

1. In apparatus equipped with a radiant rays source and a radiographicfilm holder thereby to take a tomogram of an object in the shape of anapproximately parabolic curve consisting of not less than two arcs ofdifferent curvatures; a head holding device comprising, in combination:a column slidably supporting the head holding device proper; a movablemember mounted on a pair of rails within a casing so as to be capable ofmoving toward and away from said column, said movable member having ameans thereby to be secured at any desired position in the course of itstravels; a pair of racks disposed in side-by-side relationship acrosssaid movable member and having their toothed surfaces opposed to eachother; a pinion provided between said racks so as to be in mesh withboth of them, said pinion having a means thereby to be turned manuallyfrom outside of said casing; a pair of rods provided downwardly at theopposite ends of said racks, each of said rods having at the lower end aflanged earrods to be inserted into the outer orifice of the ear; a chinrest provided to a holding member so as to be vertically movable, saidholding member being installed in a supporting portion of said casing soas to be movable toward and away from said column and to be fixed at anydesired position in the course of its travels; and a head supportincluding means for adjustment of its position in both vertical andhorizontal directions.
 2. A head holding device as claimed in claim 1,in which said holding member is provided with an indicator means, thecalibrations for which are given on said supporting portion, and saidholding member is provided with another set of calibrations for saidchin rest connected slidably thereto, whereby a setting of said chinrest in both horizontal and vertical directions can be read numerically.3. A head holding device as claimed in claim 1, in which said flangedear-rods are transparent.
 4. A head holding device as claimed in claim3, in which illuminating means are provided in the hollowed interiors ofsaid transparent flanged ear-rods.
 5. A head holding device as claimedin claim 1, in which said movable member is provided with an indicatormeans capable of indicating its position in directions toward and awayfrom said column.
 6. A head holding device as cLaimed in claim 1, inwhich said vertical rods are calibrated for indication of the heights ofsaid ear-rods provided slidably thereto.